IRJET- Design of Desiccant Integrated Solar Dryer for Cashew Drying for Small Scale Farmers

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International Research Journal of Engineering and Technology (IRJET)

e-ISSN: 2395-0056

Volume: 08 Issue: 02 | Feb 2021

p-ISSN: 2395-0072

www.irjet.net

 Insulator – It was used to lower the heat loss from the solar air heater. Here, timber was used as an insulator because of its low thermal conduction of 0.1442 W/mK.

(SAH) is needed for heating the process air supplied by the blower. India is one of the major cashew nut producers and exporters. The overall cashew production in the world is 4,152,315 metric tons per annum. In that, India contributes about 6,8,000 metric tons of cashew nut per annum (Food and Agriculture Organization, 2012). Tamil Nadu contributes about 9 % of the cashew production in which Cuddalore contributes around 47% i.e. 22,046 metric ton per annum [3].

 Desiccant – The desiccant has the higher potential to absorb/adsorb high moisture content from the processing air which is required for uniform and efficient solar drying. The desiccant will undergo two process cycles, 1. Adsorption/Absorption 2. Regeneration. During the first cycle it will absorb/adsorb moisture from processing air and during the second cycle the regeneration of desiccant material will be taking place under certain conditions.

Cashew processing comprises 8 steps like drying of raw cashew nut, Steaming, Cutting and Separation of shell, Drying of Kernel, Kernel cooling, Peeling of Kernel, Grading and Packing [4]. Among the eight steps in the cashew processing industry (which uses electric dryer for drying), the drying of cashew kernel is an energy intensive process which consumes around 575.64 MJ/1000 kg of raw nuts/180 kg batch [4] . The small scale farmers can produces around 800 kg of cashew nut per annum. They can rarely adopt the fossil fuel powered dryer due to its large initial and running cost. In order to overcome the limitations of the fossil fuel powered dryers the solar dryer can be used instead of it for drying the cashew nut.

Here, the silica gel was selected as the desiccant. The volume of the drying chamber was calculated as 35,400” in cubic inch. In general, 1 unit of desiccant can absorb 3 grams of water vapor at 20 % RH and 6 grams of water vapor at 40% of RH at 77 ᵒC. 1 unit of is equal to 32-33 grams of desiccant. The Silica gel can absorb moisture at maximum capacity of 35 % by its weight when exposed at 25 ᵒC and 80% RH. Therefore, the total unit required for the calculated volume of the drying chamber was 30 units, which means approximately 1 kg of Silica gel was needed. The quantity of desiccant used should be higher than the required rather than low amount.  Galvanized wire mesh was used for covering the entry and exit of the air in the solar collector and drying chamber to prevent the entry of insects and rodents into the dryer.

2. MATERIAL AND METHODOLOGY 2.1 Material

 The timber of 5 mm thickness was used as a separator for desiccant from the drying chamber.

The following were the materials which were utilized for the design consideration of forced convection updraft solar dryer.

 Nails and glues.

 Absorber Plate - The absorber plate should be capable of retaining more solar energy and should have high thermal conductivity. The effectiveness of the solar collector mainly depends on the properties of the absorber plate. It should be coated with black paint to increase the absorptance of the absorber. Here, aluminium with 4 cm thickness was used as the absorber plate over copper due to its cost efficient and high corrosion resistance.

 Hinges and handle for the drying chamber door.  Black paint for higher absorption and thermal conductivity of the absorber plate.  Galvanized wire mesh for the trays on which the cashew kernels are placed.

2.2 Climate data collection

 Cover plate (glass) – The cover plate’s main purpose is to lower the convective heat losses from the top of the solar collector. It should have a higher transmittance of solar radiation with low absorptance for high efficiency and should not deteriorate with time. The Glass was used as cover plate. Some plastic material could also use but it will deteriorate shortly. Here, the glass plate with 4mm is used because of its higher efficiency.

The indirect solar dryer was designed for the location Cuddalore, Tamil Nadu (India) with Longitude of 79.533 ᵒ E and Latitude of 11.7046 ᵒN. Cuddalore is a moderate climate district with hot summer and cold winter. The available solar radiation all-over the year on flat surfaces in Cuddalore was found to be 582 W/m2 [5]. With the tilt angle of 21.7046ᵒ towards south direction of the solar collector, the total solar radiation available on the titled surface was calculated as 613 W/m2. The above mentioned geographical details needed for the design were collected from PV syst software from Meteonorm 7.3.

 Enclosure – It was mainly used to enclose all the components of the solar collector. Steel, aluminium, fiberglass and wood are some of the examples of enclosure. It also lowers the heat losses from the bottom of the solar collector. Generally, a layer of insulator is placed at the bottom of the absorber plate to reduce the heat loss.

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